Numerical simulation of the effect of injection sites arrangement on the thermal ablation in the magnetic fluid hyperthermia

Abstract

Magnetic hyperthermia ablates malignant cells by the heat-dissipating from magnetic nanoparticles (MNPs) when subjects to an alternate magnetic field. To reveal the heat transfer mechanism for magnetic fluid hyperthermia (MFH) and analyze the effect of injection site arrangement on the temperature distribution during magnetic fluid hyperthermia. A three-dimensional multi-physical model was established to obtain the temperature distribution of the treated tumor tissues, the concentration distribution of magnetic fluid, effective treatment volume (Veff), and thermal damage fraction of the tumor. The treatment temperature distribution for a proposed physical model is predicted by solving Pennes bio-heat transfer equation using the finite element method, in which a heat source in form of a Gaussian distribution is used as the power dissipation of MNPs. The results demonstrate that the size of the heat source has a greater effect on the maximum temperature of the heat source center under a single injection site. Additionally, it found that the effective treatment volume is not the sum of the effective treatment volumes at each injection site for the multisite injections. The effective treatment volume shows a strong nonlinear increase with the number of injection site increases compared with the single injection site. The multisite injection can significantly increase the effective treatment volume during the hyperthermia process and achieve the effect of agglomeration heating. For eight injection sites, the optimal effective treatment volume change rate (εV) reached 94.7%. Additionally, the temperature distribution uniformity of eight injection sites is greatly improved compared with other injection site arrangements under an equal dose. The damage fraction of single site injection from 0.12 up to 0.55 when the magnetic hyperthermia treatment time increases from 0 to 40 min while the damage fraction of eight sites injection from 0.23 up to 0.94. In the clinical treatment process, the distance between the injection sites and the time of magnetic hyperthermia can be reasonably arranged according to the size, shape, and type of the tumor, which not only can obtain a good thermal ablation effect but can effectively reduce the thermal damage to normal tissues.